Aorta homogenates and aorta cell cultures will be used to study farry acid synthesis and modification. The program is designed to yield information about how arterial lipid metabolism changes as fatty lesions develop in atherosclerosis, to identify which components of the milieu to which the artery is exoised influence changes in arterial metabolism, and to elucidate the mechanisms by which these changes are effected. The acyl specificity of the mitochondrial and microsomal fatty acid elongating enzymes will be measured. The presence or absence of fatty acid desaturation in aorta will be established. The rates of de novo synthesis, mitochondrial elongation, microsomal elongation, activation, and desaturation of fatty acids will be measured in subcellular fractions from normal and atherosclerotic human tissue. Finally, aorta cells and aorta segments will be maintained in culture, and the effect of modifying the lipid composition of the milieu on the processes of fatty acid synthesis and modification will be measured.